feature(function): add custom functions documentation for AWS Amplify-backend

[MarlonJD]

… Gen 2 @aws-amplify/amplify-backend/1602

Description of changes:

Add custom runtime documents, it's required for #1602

Related GitHub issue

#1543, #1486

Instructions

Which product(s) are affected by this PR (if applicable)?

• amplify-backend
• amplify-ui
• amplify-studio
• amplify-hosting
• amplify-libraries

Which platform(s) are affected by this PR (if applicable)?

• JS
• Swift
• Android
• Flutter
• React Native

Please add the product(s)/platform(s) affected to the PR title
amplify-backend

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[sobolk]

I left two comments around docker and go. But I suggest to wait until @josefaidt gets a chance to review this before making changes.

[sobolk]

Suggested change

	<Callout warning>
	**Note:** Custom runtimes are not supported in Amplify Functions directly. If you need docker support to use a custom runtime for example in Python, Docker is not supported in Amplify Hosting and Amplify backend auto build. You shouldn't use docker build in your function.There is an example of how to use python in a lambda function in the without Docker section below.
	</Callout>
	<Callout warning>
	**Note:** [Fullstack Git-based environments](https://docs.amplify.aws/react/how-amplify-works/concepts/#fullstack-git-based-environments) do not support Docker for functions bundling out of the box.
	</Callout>

[josefaidt]

Suggested change

	AWS Amplify Gen 2 Functions are AWS Lambda functions that can be used to perform tasks and customize workflows in your Amplify app.Functions can be written in Node.js, Python, Go, or any other language supported by AWS Lambda:
	AWS Amplify Gen 2 functions are AWS Lambda functions that can be used to perform tasks and customize workflows in your Amplify app. Functions can be written in Node.js, Python, Go, or any [other language supported by AWS Lambda](https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html).

[josefaidt]

Suggested change

	Technically, you can use any language supported by AWS Lambda. These are NodeJS, Python, Java, .NET, Ruby.
	To use other languages in Lambda, such as Go or Rust, use an OS-only runtime.

[josefaidt]

Suggested change

	In this guide, you will learn how to create python and golang functions in Amplify Functions.
	In this guide, you will learn how to create Python and Go functions with Amplify functions. The examples shown in this guide do not use Docker to build functions. Instead, the examples use commands that run on your host system to build, and as such require the necessary tooling for the language you are using for your functions.

separately we should include a troubleshooting guide for docker errors encountered when using Amplify Hosting to build and deploy backends, then link out from here

[josefaidt]

Suggested change

	# Python functions
	To get started, create a new directory and a resource file, `amplify/functions/say-hello/resource.ts`. Then, define the Function with `defineFunction`:
	## Python
	To get started, create a new directory and a resource file, `amplify/functions/say-hello/resource.ts`. Then, define the function with `defineFunction`:

[josefaidt]

Suggested change

	import { defineFunction } from "@aws-amplify/backend";
	import { DockerImage, Duration } from "aws-cdk-lib";
	import { Code, Function, Runtime } from "aws-cdk-lib/aws-lambda";
	import { execSync } from "child_process";
	import * as path from "path";
	import { fileURLToPath } from "url";
	import { execSync } from "node:child_process";
	import * as path from "node:path";
	import { fileURLToPath } from "node:url";
	import { defineFunction } from "@aws-amplify/backend";
	import { DockerImage, Duration } from "aws-cdk-lib";
	import { Code, Function, Runtime } from "aws-cdk-lib/aws-lambda";

ordering nit for node imports

[josefaidt]

Suggested change

	The handler file _must_ export a function named "handler". This is the entry point to your function. For more information on writing functions, refer to the [AWS documentation for Lambda function handlers using python](https://docs.aws.amazon.com/lambda/latest/dg/python-handler.html).
	The handler file _must_ export a function named "handler". This is the entry point to your function. For more information on writing functions, refer to the [AWS documentation for Lambda function handlers using Python](https://docs.aws.amazon.com/lambda/latest/dg/python-handler.html).

casing nit for proper noun

[josefaidt]

Suggested change

	If you need python packages, you can add them to a `requirements.txt` file in the same directory as your handler file. The `bundling` option in the `Code.fromAsset` method will install these packages for you.
	If you need Python packages, you can add them to a `requirements.txt` file in the same directory as your handler file. The `bundling` option in the `Code.fromAsset` method will install these packages for you.

[josefaidt]

is this dependency still relevant?

[josefaidt]

Suggested change

	create a new directory and a resource file, `amplify/functions/say-hello/resource.ts`. Then, define the Function with `defineFunction`:
	Create a new directory and a resource file, `amplify/functions/say-hello/resource.ts`. Then, define the function with `defineFunction`:

[josefaidt]

Suggested change

	# Go functions
	## Go

[josefaidt]

Suggested change

	import { defineFunction } from "@aws-amplify/backend";
	import { DockerImage, Duration } from "aws-cdk-lib";
	import { Code, Function, Runtime } from "aws-cdk-lib/aws-lambda";
	import { execSync } from "child_process";
	import * as path from "path";
	import { fileURLToPath } from "url";
	import { execSync } from "node:child_process";
	import * as path from "node:path";
	import { fileURLToPath } from "node:url";
	import { defineFunction } from "@aws-amplify/backend";
	import { DockerImage, Duration } from "aws-cdk-lib";
	import { Code, Function, Runtime } from "aws-cdk-lib/aws-lambda";

[josefaidt]

Suggested change

	```bash title="terminal"
	```bash title="Terminal" showLineNumbers={false}

[josefaidt]

Suggested change

	```bash title="terminal"
	```bash title="Terminal" showLineNumbers={false}

[josefaidt]

Suggested change

	# Common steps for all languages
	Lastly, this function needs to be added to your backend.
	## Common steps for all languages
	Regardless of the language used, your function needs to be added to your backend.

[josefaidt]

Suggested change

	Now when you run `npx ampx sandbox` or deploy your app on Amplify, it will include your Function.
	Now when you run `npx ampx sandbox` or deploy your app on Amplify, it will include your function.

[josefaidt]

can we reword this to remove the language around strongly typed handlers? that will be a typescript-specific feature

[josefaidt]

Suggested change

	'Use another AWS Lambda runtimes like python, golang to perform tasks and customize workflows.',
	'Use another AWS Lambda runtimes like Python, Golang to perform tasks and customize workflows.',

[josefaidt]

Hey @MarlonJD thank you for taking the time to write this up!! I left a few comments to adjust some of the language used but overall this looks great!